/* This is a public domain base64 implementation written by WEI Zhicheng. */

#include "base64.h"

#define BASE64_PAD '='
#define BASE64DE_FIRST '+'
#define BASE64DE_LAST 'z'

/* BASE 64 encode table */
static const char base64en[] = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
    'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
    'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/',
};

/* ASCII order for BASE 64 decode, 255 in unused character */
static const unsigned char base64de[] = {
    /* nul, soh, stx, etx, eot, enq, ack, bel, */
    255, 255, 255, 255, 255, 255, 255, 255,

    /*  bs,  ht,  nl,  vt,  np,  cr,  so,  si, */
    255, 255, 255, 255, 255, 255, 255, 255,

    /* dle, dc1, dc2, dc3, dc4, nak, syn, etb, */
    255, 255, 255, 255, 255, 255, 255, 255,

    /* can,  em, sub, esc,  fs,  gs,  rs,  us, */
    255, 255, 255, 255, 255, 255, 255, 255,

    /*  sp, '!', '"', '#', '$', '%', '&', ''', */
    255, 255, 255, 255, 255, 255, 255, 255,

    /* '(', ')', '*', '+', ',', '-', '.', '/', */
    255, 255, 255, 62, 255, 255, 255, 63,

    /* '0', '1', '2', '3', '4', '5', '6', '7', */
    52, 53, 54, 55, 56, 57, 58, 59,

    /* '8', '9', ':', ';', '<', '=', '>', '?', */
    60, 61, 255, 255, 255, 255, 255, 255,

    /* '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G', */
    255, 0, 1, 2, 3, 4, 5, 6,

    /* 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', */
    7, 8, 9, 10, 11, 12, 13, 14,

    /* 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', */
    15, 16, 17, 18, 19, 20, 21, 22,

    /* 'X', 'Y', 'Z', '[', '\', ']', '^', '_', */
    23, 24, 25, 255, 255, 255, 255, 255,

    /* '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g', */
    255, 26, 27, 28, 29, 30, 31, 32,

    /* 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', */
    33, 34, 35, 36, 37, 38, 39, 40,

    /* 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', */
    41, 42, 43, 44, 45, 46, 47, 48,

    /* 'x', 'y', 'z', '{', '|', '}', '~', del, */
    49, 50, 51, 255, 255, 255, 255, 255};

unsigned int base64_encode(const unsigned char* in, unsigned int inlen, char* out) {
  int s;
  unsigned int i;
  unsigned int j;
  unsigned char c;
  unsigned char l;

  s = 0;
  l = 0;
  for (i = j = 0; i < inlen; i++) {
    c = in[i];

    switch (s) {
      case 0:
        s = 1;
        out[j++] = base64en[(c >> 2) & 0x3F];
        break;
      case 1:
        s = 2;
        out[j++] = base64en[((l & 0x3) << 4) | ((c >> 4) & 0xF)];
        break;
      case 2:
        s = 0;
        out[j++] = base64en[((l & 0xF) << 2) | ((c >> 6) & 0x3)];
        out[j++] = base64en[c & 0x3F];
        break;
    }
    l = c;
  }

  switch (s) {
    case 1:
      out[j++] = base64en[(l & 0x3) << 4];
      out[j++] = BASE64_PAD;
      out[j++] = BASE64_PAD;
      break;
    case 2:
      out[j++] = base64en[(l & 0xF) << 2];
      out[j++] = BASE64_PAD;
      break;
  }

  out[j] = 0;

  return j;
}

unsigned int base64_decode(const char* in, unsigned int inlen, unsigned char* out) {
  unsigned int i;
  unsigned int j;
  unsigned char c;

  if (inlen & 0x3) {
    return 0;
  }

  for (i = j = 0; i < inlen; i++) {
    if (in[i] == BASE64_PAD) {
      break;
    }
    if (in[i] < BASE64DE_FIRST || in[i] > BASE64DE_LAST) {
      return 0;
    }

    c = base64de[(unsigned char)in[i]];
    if (c == 255) {
      return 0;
    }

    switch (i & 0x3) {
      case 0:
        out[j] = (c << 2) & 0xFF;
        break;
      case 1:
        out[j++] |= (c >> 4) & 0x3;
        out[j] = (c & 0xF) << 4;
        break;
      case 2:
        out[j++] |= (c >> 2) & 0xF;
        out[j] = (c & 0x3) << 6;
        break;
      case 3:
        out[j++] |= c;
        break;
    }
  }

  return j;
}
